1. Field of the Invention
The present invention relates to an autofocus camera.
2. Description of the Related Art
There are focal point detection methods known in the related art adopted in cameras to detect the state of focal point position adjustment of a photographic lens based upon image-capturing signals output from an image-capturing element such as a CCD that captures a subject image. In the so-called hill-climbing method among those camera focal point detectionmethods, while the focus lens moves forward/backward along the optical axis, a position at which the data corresponding to the high frequency component of the image-capturing signal, i.e., the focal point evaluation value, indicate the maximal value is detected as the focused position.
When the subject contains a light source with a high brightness level or the like, image-capturing signals corresponding to the light source become saturated. The saturated image-capturing signals indicate a uniform saturation-level value. Generally speaking, such image-capturing signals indicating a uniform level do not contain a significant high frequency component, and for this reason, it is difficult to accurately detect the focused position with saturated image-capturing signals.
Accordingly, Japanese Laid Open Patent Publication No. H 6-205268 discloses a camera that switches the low range cutoff frequency of a filter that allows the high-frequency component of image-capturing signals to pass through when capturing an image with a very bright subject. This camera counts the number of scanning lines in which the brightness signals indicate values greater than a predetermined value and judges that the brightness level of the subject is high when the scanning line count exceeds a predetermined number. If the brightness level of the subject is judged to be high, the camera switches to a high pass filter that cuts off the low frequency component of the brightness signals to a greater extent than the extent to which the low frequency component is cut off when the brightness level of the subject is not judged to be high. After making this switch, the camera detects the focused position by extracting the high-frequency component of the brightness signals having passed through the high pass filter.
However, under certain circumstances, the focal point evaluation value may still peak at the-focused position even when the brightness of the subject is high. In such a case, if the low range cutoff frequency of the filter which allows the high-frequency component of image-capturing signals to pass through is switched, the focused position cannot be accurately detected.